Update AddModuleWatermark

src/main/kotlin/fi/aalto/cs/apluscourses/utils/callbacks/AddModuleWatermark.kt

@@ -4,50 +4,63 @@ import com.intellij.openapi.project.Project
 import fi.aalto.cs.apluscourses.model.component.Module
 import fi.aalto.cs.apluscourses.model.people.User
 import fi.aalto.cs.apluscourses.services.course.CourseManager
+import kotlinx.datetime.Clock
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toLocalDateTime
 import java.io.IOException
 import java.io.UncheckedIOException
 import java.nio.file.Files
 import java.nio.file.Path
+import java.security.MessageDigest
 import java.util.Locale
-import java.util.function.Supplier
 import java.util.stream.Collectors
 
 object AddModuleWatermark {
     private const val ENCODING_LINE = "# -*- coding: utf-8 -*-"
     private const val ENCODING_LINE_WITH_UNICODE =
         "#\u200b\u200c\u200b\u200b\u200b\u200b\u200c\u200c\u200b\u200c\u200b\u200c\u200c\u200b *-* coding: utf-8 *-*"
 
-    private fun createWatermark(userId: Long): String {
-        return java.lang.Long.toBinaryString(userId)
-            .replace('1', '\u200b')
-            .replace('0', '\u200c')
-    }
-
     @Throws(IOException::class)
     private fun addWatermark(path: Path, user: User?) {
         val userId = user?.aplusId ?: 0
         val studentId = user?.studentId ?: "---"
         val studentName = user?.userName ?: "---"
 
-        val watermark = createWatermark(userId)
+        val newLines = Files.lines(path).use { lineStream ->
+            lineStream.filter { line ->
+                line != ENCODING_LINE && line != ENCODING_LINE_WITH_UNICODE
+            }.collect(Collectors.toCollection { mutableListOf<String>() })
+        }
+
+        val date = Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault())
 
-        Files.lines(path).use { lineStream ->
-            val newLinesMutable = lineStream.map<String> { line: String ->
-                if (line == ENCODING_LINE || line == ENCODING_LINE_WITH_UNICODE) {
-                    return@map ""
-                } else if (line.trim { it <= ' ' }.startsWith("#")) {
-                    return@map line.replaceFirst("#".toRegex(), "#$watermark")
-                }
-                line
-            }.collect(
-                Collectors.toCollection<String, java.util.ArrayList<String>>(
-                    Supplier<java.util.ArrayList<String>> { ArrayList() })
+        newLines.addAll(
+            0, listOf(
+                ENCODING_LINE,
+                "# Nimi: $studentName",
+                "# Opiskelijanumero: $studentId",
+                "# Data Structures and Algorithms Y CS-A1141",
+                "# Date: ${date.dayOfMonth}/${date.monthNumber}/${date.year}"
             )
-            newLinesMutable.add(0, ENCODING_LINE)
-            newLinesMutable.add(1, "# Nimi: $studentName")
-            newLinesMutable.add(2, "# Opiskelijanumero: $studentId")
-            Files.write(path, newLinesMutable)
-        }
+        )
+
+        val hash = generateHash(userId.toString())
+
+        newLines.addAll(
+            listOf(
+                "",
+                "# Do not remove or modify this",
+                "# Unique hash: $hash"
+            )
+        )
+
+        Files.write(path, newLines)
+    }
+
+    private fun generateHash(input: String): String {
+        val md = MessageDigest.getInstance("SHA-256")
+        val bytes = md.digest(input.toByteArray())
+        return bytes.joinToString("") { "%02x".format(it) }
     }
 
     /**